Liquid crystal display device

ABSTRACT

An in-cell type liquid crystal display device includes a first unit that detects whether a touch is present, or not, on the basis of a current flowing in a plurality of detection electrodes when a touch panel scanning voltage is applied to counter electrodes of each of M (M≥2) divided blocks, and a second unit that detects noise on the basis of a current flowing in the plurality of detection electrodes, assuming that an (M+1)th counter electrode is present for the counter electrodes of each of the M divided blocks, and assuming that a touch panel scanning voltage synchronous with the touch panel scanning voltage applied to the counter electrodes of each of the M divided blocks is applied to the (M+1)th counter electrode.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.14/025,103, filed on Sep. 12, 2013. Further, this application claimspriority from Japanese application JP2012-209837 filed on Sep. 24, 2012,the content of which is hereby incorporated by reference into thisapplication.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a liquid crystal display device, andmore particularly to an effective technique applied to a liquid crystaldisplay device of an in-cell system incorporating a touch panel.

2. Description of the Related Art

Display devices having a device (hereinafter, referred to as touchsensor or touch panel) that enters information by conducting touchoperation (contact press operation, hereinafter referred to simply astouch) on a display screen through a user s finger or a pen are used inmobile electronic devices such as a PDA or a mobile terminal, a varietyof home electric appliances, and automated teller machines.

As the touch panel of this type, there has been known a electrostaticcapacitance system that detects a change in capacity of a touchedportion.

As the electrostatic capacitance type touch panel, there has been knowna so-called in-cell type liquid crystal display device with a touchpanel function into a liquid crystal display panel.

In the in-cell type liquid crystal display device, scanning electrodesof the touch panel are used by dividing a counter electrode (also calledcommon electrode) formed on a first substrate (so-called TFT substrate)configuring a liquid crystal display panel.

SUMMARY OF THE INVENTION

In the in-cell type liquid crystal display device, a touch panel drivefrequency is set to be equal to a horizontal scanning frequency (touchpanel drive frequency=horizontal scanning frequency of liquid crystaldisplay panel) of the liquid crystal display panel. As a result, displaynoise of the liquid crystal display panel which becomes a problem in arelated art out-cell type touch panel can be avoided by a timing designto improve a false detection problem.

On the other hand, from the viewpoint of exogenous noise, because thetouch panel drive frequency has no degree of freedom of setting, whenthe exogenous noise having the noise frequency substantially equal tothe integral multiple of the horizontal scanning frequency (exogenousnoise frequency≈integral multiple of horizontal scanning frequency) isentered, an integrating circuit within a detector circuit induces falseintegration to generate ghost.

For example, as illustrated in FIG. 20, when an inexpensive charger isconnected to a mobile terminal with the touch panel, a fictional touchghost (B in FIG. 20) is induced at a position different from a touchposition (A in FIG. 20) due to noise generated from the charger, thatis, so-called AC charger noise. Because the AC charger noise is in-phasenoise, a problem such as a false detection does not arise in a non-touchstate even during charging operation.

The present invention has been made to solve the problem with therelated art, and therefore an object of the present invention is toprovide a technique in which an influence of the fictional touch ghoston the touch detection can be reduced in a liquid crystal display devicewith a touch panel function.

The above and other objects, and novel features of the present inventionwill become apparent from the description of the present specificationand attached drawings.

An outline of typical features in the invention disclosed in the presentapplication will be described in brief as follows.

(1) A liquid crystal display device including a liquid crystal displaypanel having a first substrate, a second substrate, and liquid crystalsandwiched between the first substrate and the second substrate in whicha plurality of pixels is arranged in a matrix,

wherein the second substrate has a plurality of detection electrodes fora touch panel,

each of the pixels has a pixel electrode and a counter electrode, thecounter electrode is divided into M blocks where M is an integer of 2 ormore (M≥2),

the counter electrodes of each of the M divided blocks are shared withthe respective pixels of a plurality of continuous display lines,

the counter electrodes of each of the M divided blocks also function asscanning electrodes of the touch panel,

a driver circuit that applies a counter voltage and a touch panelscanning voltage to the counter electrodes of each of the M dividedblocks, and a detector circuit that detects whether a touch is present,or not, on the basis of a current flowing in the plurality of detectionelectrodes are provided,

the driver circuit sequentially applies a touch panel scanning voltageto the counter electrodes of each of the M divided blocks,

the detector circuit includes a first unit that detects whether thetouch is present, or not, on the basis of a current flowing in theplurality of detection currents, a second unit that detects noise on thebasis of a current flowing in the plurality of detection electrodes,assuming that an (M+1)^(th) counter electrode is present for the counterelectrodes of each of the M divided blocks, and assuming that a touchpanel scanning voltage synchronous with the touch panel scanning voltageapplied to the counter electrodes of each of the M divided blocks isapplied to the (M+1)^(th) counter electrode, and a third unit thatidentifies a fictional touch caused by the noise when the noise isdetected by the second unit,

in a touch detecting process, a normal touch position detecting processis executed when no noise is detected in the second unit, a touchposition detecting process is executed with reference to the fictionaltouch identified by the third unit if the fictional touch caused by thenoise can be identified by the third unit when the noise is detected inthe second unit, and the touch position detecting process is notexecuted if the fictional touch caused by the noise cannot be identifiedby the third unit when the noise is detected in the second unit.

(2) In the item (1), the detector circuit includes a plurality ofintegrating circuits provided every plural detection electrodes, and anAD converter that converts an output voltage of the plurality ofintegrating circuits into digital data,

each of the integrating circuits integrates the current flowing in therespective detection electrodes for each of the counter electrodes ofeach of the M divided blocks and the fictional (M+1)^(th) counterelectrode when the touch panel scanning voltage is applied to thecounter electrodes of each of the M divided blocks, and when a fictionaltouch panel scanning voltage is applied to the frictional (M+1)^(th)counter electrode,

the first unit determines that a touch is present when a value of thedigital data obtained by converting an integral value of the pluralityof integrating circuits for each of the counter electrodes of each ofthe M divided blocks by the AD converter is a value between a firstoperating point and the most significant bit, and when a differencebetween the value of the digital data and the first operating point islarger than a given first threshold value, and determines that the touchis absent in other cases, with a value closer to the least significantbit than an intermediate value between the least significant bit and themost significant bit in the digital data converted by the AD converteras the first operating point,

the second unit determines that noise is present when a value of thedigital data obtained by converting an integral value of the pluralityof integrating circuits for the fictional (M+1)^(th) counter electrodeby the AD converter is a value between a second operating point and theleast significant bit, and when a difference between the value of thedigital data and the second operating point is larger than a givensecond threshold value, and

the third unit allows the digital data obtained by converting theintegral value of the integrating circuits corresponding to thedetection electrode in which the noise is detected by the second unitfor each of the counter electrodes of each of the M divided blocks bythe AD converter to pass through an averaging filter, and determines anelectrode having a maximum data value among the data that has passedthrough the averaging filter as an actual touch electrode, andidentifies, as the fictional touch electrode, an electrode in which adata value is a value between the maximum value and the leastsignificant bit, and a difference between the data value and the maximumvalue is larger than a given third threshold value.

The advantages obtained by the typical features of the inventiondisclosed in the present application will be described in brief below.

According to the present invention, in the liquid crystal display devicewith the touch panel function, an influence of the fictional touch ghoston the touch detection can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view illustrating an outlineconfiguration of an in-cell type liquid crystal display deviceincorporating a touch panel into a liquid crystal display panel;

FIG. 2 is a diagram illustrating counter electrodes and detectionelectrodes in the liquid crystal display device illustrated in FIG. 1;

FIG. 3 is a partially enlarged schematic cross-sectional viewillustrating a display unit of the liquid crystal display deviceillustrated in FIG. 1;

FIG. 4 is a block diagram illustrating an overall outline configurationof a touch panel in an in-cell type liquid crystal display device whichis a preamble of the present invention;

FIG. 5 is a diagram illustrating a detection principle of the touchpanel in the in-cell type liquid crystal display device which is thepreamble of the present invention;

FIG. 6 is a timing chart illustrating touch detecting operation of thetouch panel in the in-cell type liquid crystal display device which isthe preamble of the present invention;

FIG. 7 is a circuit diagram illustrating a more specific circuitconfiguration of a detector circuit illustrated in FIG. 4;

FIG. 8 is a timing chart illustrating the operation of the circuitillustrated in FIG. 7;

FIG. 9 is a diagram illustrating timing in touch panel detectingoperation and pixel write operation;

FIG. 10 is a timing chart illustrating liquid crystal display paneldriving operation and sensor electrode driving operation in the in-celltype liquid crystal display device which is the preamble of the presentinvention;

FIG. 11 is a diagram illustrating the specifications of registersillustrated in FIG. 4;

FIG. 12 is a diagram illustrating a touch panel scanning timing in thein-cell type liquid crystal display device which is the preamble of thepresent invention;

FIG. 13 is a diagram illustrating a touch panel scanning timing in amodified example of the in-cell type liquid crystal display device whichis the preamble of the present invention;

FIG. 14 is a diagram illustrating a noise detection method of the touchpanel in the in-cell type liquid crystal display device according to anembodiment of the present invention;

FIG. 15 is a graph illustrating RAW data when there is no noise detectedby the detection electrodes through a noise detection method of thetouch panel according to an embodiment of the present invention;

FIG. 16 is a graph illustrating RAW data of the noise having a noisefrequency other than an integral multiple of a horizontal scanningfrequency (exogenous noise frequency≠integral multiple of horizontalscanning frequency), which is detected by the detection electrodesthrough the noise detection method of the touch panel according to theembodiment of the present invention;

FIG. 17 is a graph illustrating RAW data of the noise having a noisefrequency substantially equal to the integral multiple of the horizontalscanning frequency (exogenous noise frequency≠integral multiple ofhorizontal scanning frequency), which is detected by the detectionelectrodes through the noise detection method of the touch panelaccording to the embodiment of the present invention;

FIGS. 18A and 18B are graphs illustrating the RAW data of the detectionelectrodes where noise is detected, and data that has passed through anaveraging filter;

FIG. 19 is a flowchart illustrating a touch position detecting processin the in-cell type liquid crystal display device according to theembodiment of the present invention; and

FIG. 20 is a diagram illustrating a fictional touch ghost occurring at aposition different from a touch position in the touch panel.

DETAILED DESCRIPTION OF THE INVENTION

In all of the drawings illustrating the embodiment, parts having thesame functions are denoted by identical symbols, and their repetitivedescription will be omitted. Also, the following embodiment does notlimit the interpretation of the claims of the present invention.

FIG. 1 is an exploded perspective view illustrating an outlineconfiguration of an in-cell type liquid crystal display deviceincorporating a touch panel into a liquid crystal display panel.

Referring to FIG. 1, reference numeral 2 denotes a first substrate(hereinafter referred to as TFT substrate), 3 is a second substrate(hereinafter referred to as CF substrate), 21 is counter electrodes(also called common electrodes), 5 is a liquid crystal driver IC, MFPCis a main flexible printed circuit board, 40 is a front window, and 53is a connection flexible printed circuit board.

In the liquid crystal display device illustrated in FIG. 1, a rearsurface side transparent conductive film (CD) on the CF substrate 3 isdivided into band-like patterns to form detection electrodes 31 of thetouch panel. Also, the counter electrodes 21 formed within the TFTsubstrate 2 is divided into band-like patterns, that is, divided into aplurality of blocks to be also used as scanning electrodes of the touchpanel. With this configuration, the touch panel substrate used in anormal touch panel is deleted. Also, in the liquid crystal displaydevice illustrated in FIG. 1, a circuit for driving the touch panel isdisposed within a liquid crystal driver IC (5).

Subsequently, a description will be given of the counter electrodes 21and the detection electrodes 31 in the liquid crystal display deviceillustrated in FIG. 1 with reference to FIG. 2.

As described above, the counter electrodes 21 are disposed on the TFTsubstrate 2, and the plurality (for example, about 32) of counterelectrodes 21 are commonly connected at both ends thereof, and connectedto a counter electrode signal line 22.

In the liquid crystal display device illustrated in FIG. 2, a bundle ofcounter electrodes 21 is also used as the scanning electrodes (TX), andthe detection electrodes 31 also configure the detection electrodes(RX).

Therefore, the counter electrode signal includes the counter voltageused for image display and the touch panel scanning voltage used fordetection of the touch position. When the touch panel scanning voltageis applied to the counter electrodes 21, a detection signal is generatedin the detection electrodes 31 which are arranged at a given intervalfrom the counter electrodes 21, and configure a capacitance. Thedetection signal is extracted to the external through detectionelectrode terminals 36.

Dummy electrodes 33 are formed on both sides of the detection electrodes31. One end of each detection electrode 31 forms the T-shaped detectionelectrode terminal 36 which is widened toward the dummy electrode 33 onone end thereof. Also, a variety of lines and terminals such as a drivercircuit input terminal 25 are formed on the TFT substrate 2 other thanthe counter electrode signal line 22.

FIG. 3 is a partially enlarged cross-sectional schematic diagramillustrating a display unit in the liquid crystal display deviceillustrated in FIG. 1.

As illustrated in FIG. 3, a pixel portion 200 is disposed on the TFTsubstrate 2. The counter electrodes 21 are used in the image display asa part of pixels. Also, a liquid crystal composition 4 is sandwichedbetween the TFT substrate 2 and the CF substrate 3. The detectionelectrodes 31 disposed on the CF substrate 3 and the counter electrodes21 disposed on the TFT substrate form a capacitance, and when the drivesignal is supplied to the counter electrodes 21, a voltage across thedetection electrodes 31 is changed.

In this situation, as illustrated in FIG. 3, when a conductive body suchas a finger 502 comes in proximity to or in contact with any detectionelectrode 31 through the front window 40, the capacitance is changed tochange the voltage generated in the detection electrode 31 as comparedwith a case in which there is no proximity to or contact with thedetection electrode 31.

Thus, a change in the capacitance generated between the counterelectrodes 21 and the detection electrodes 31 formed on the liquidcrystal display panel 1 is detected. This makes it possible to providethe liquid crystal display panel with the function of the touch panel.

FIG. 4 is a block diagram illustrating an overall outline configurationof the touch panel in the in-cell type liquid crystal display devicewhich is a preamble of the present invention.

Referring to FIG. 4, 101 denotes an LCD driver, 102 is a sequencer, 103is a touch panel scanning voltage generator circuit, 104 is a delaycircuit, 106 is a decoder circuit, 107 is a touch panel, 108 is adetector circuit, and 1051, 1052 are registers.

The touch panel 107 is formed with an electrode pattern (scanningelectrodes Tx1 to Tx5, detection electrodes Rx1 to Rx5) which is asensor terminal for detecting a user s touch.

In the in-cell type liquid crystal display device which is the preambleof the present invention, because the touch panel function is installedinto the liquid crystal display panel, the band-like counter electrodes21 illustrated in FIG. 2 are also used as the scanning electrodes (Tx),and the detection electrodes 31 configure the detection electrodes (Rx).

The LCD driver 101 transmits synchronizing signals (verticalsynchronizing signal (Vsync) and horizontal synchronizing signal(Hsync)) for displaying an image on the liquid crystal display panel tothe sequencer 102.

The sequencer 102 controls the touch panel scanning voltage generatorcircuit 103, the delay circuit 104, the decoder circuit 106, and thedetector circuit 108 to control the timing of the touch detectingoperation.

The touch panel scanning voltage generator circuit 103 generates andoutputs a touch panel scanning voltage (Vstc) for driving the scanningelectrodes Tx1 to Tx5.

The delay circuit 104 delays the touch panel scanning voltage (Vstc)input from the touch panel scanning voltage generator circuit 103 by theamount of delay instructed from the sequencer 102. The sequencer 102determines the amount of delay on the basis of a parameter stored inregisters (1051, 1052).

The register 1051 is a register that stores a unit delay time therein,and the register 1052 stores a maximum delay time therein. The unitdelay time stored in the register 1051 is a unit time by which the touchpanel scanning voltage (Vstc) is delayed, which is a parameter fordetermining a drive period of the touch panel scanning voltage (Vstc).

The maximum delay time stored in the register 1052 is a maximum time bywhich the touch panel scanning voltage (Vstc) is delayed, which is aparameter for defining an allowable range in which timing of the touchpanel scanning voltage (Vstc) is varied.

The decoder circuit 106 is an analog switch (demultiplexer) that outputsthe touch panel scanning voltage (Vstc) to one scanning electrode amongthe scanning electrodes Tx1 to Tx5.

The detector circuit 108 detects an interelectrode capacity (mutualcapacity) at intersections of one scanning electrode applied with thetouch panel scanning voltage (Vstc) among the scanning electrodes Tx1 toTx5, and the respective detection electrodes Rx1 to Rx5.

FIG. 5 is a diagram illustrating a detection principle of the touchpanel in the in-cell type liquid crystal display device which is thepreamble of the present invention.

FIG. 6 is a timing chart illustrating touch detecting operation in thein-cell type liquid crystal display device which is the preamble of thepresent invention.

The sequencer 102 controls the touch panel scanning voltage generatorcircuit 103, and sequentially applies the touch panel scanning voltage(Vstc) to the scanning electrodes Tx1 to Tx5 in synchronization with thevertical synchronizing signal (Vsync) and the horizontal synchronizingsignal (Hsync). In this example, as illustrated in FIGS. 5 and 6, therespective scanning electrodes are applied with touch panel scanningvoltage (Vstc) by plural times (eight times in FIG. 6).

As illustrated in FIG. 6, the detector circuit 108 integrates currentsflowing into the respective detection currents Rx1 to Rx5 (integrationin a negative direction in FIG. 6), and records arrived voltage values(ΔVa, ΔVb).

When the finger (conductor) touches a neighborhood of the intersectionsbetween the scanning electrodes (Tx) and the detection electrodes (Rx),a current also flows into the finger. For that reason, the voltage valueof the integration result is changed.

For example, in FIG. 6, because no finger is present in the vicinity ofan intersection between the scanning electrode (Tx1) and the detectionelectrode (RxN) (state where a touch is absent, indicated by NA in FIG.6), a voltage obtained by integrating a current flowing in the detectionelectrode becomes an untouched level (LA).

On the contrary, because the finger is present in the vicinity of anintersection between the scanning electrode (Tx2) and the detectionelectrode (RxN) (state where a touch is present, indicated by NB in FIG.6), a current also flows into the finger, and the voltage obtained byintegrating the current flowing in the detection electrode becomeshigher than the untouched level (LA). The touch position can be detectedby a variation of the voltage (touch signal).

FIG. 7 is a circuit diagram illustrating a more specific circuitconfiguration of the detector circuit 108 illustrated in FIG. 4.

FIG. 8 is a timing chart illustrating the operation of the circuitillustrated in FIG. 7.

Referring to FIG. 7, reference numeral 10 denotes an integratingcircuit, 11 is a sample-and-hold circuit, 12 is an AD converter of 10bits, and 13 is a memory (RAM) that stores data (hereinafter referred toas RAW data) output from the AD converter 12.

Hereinafter, the operation of the circuit illustrated in FIG. 7 will bedescribed with reference to FIG. 8. Referring to FIG. 8, Hsync is ahorizontal synchronizing signal. (1) Before currents flowing in therespective detection electrodes (Rx1 to Rxn) are detected (integrated),switches (S1) turn on to reset the integrating circuit 10. Also,switches (S3) turn on to reset the respective detection electrodes (Rx1to Rxn) (period A1 in FIG. 8).

When a reference voltage (VREF) is set to 4 V (VREF=4V), an output ofthe integrating circuit 10 becomes 4V, and respective detectionelectrodes (Rx1 to Rxn) are precharged to 4V. (2) Then, after the switch(S1) and the switch (S3) have been turned off, a touch panel scanningvoltage (Vstc) is output from one of the scanning electrodes Tx1 to Txm,and the switch (S2) turns on to conduct the integration insynchronization with the output of the touch panel scanning voltage(Vstc) (period B1 in FIG. 8).

As a result, a current flows in a path of one of the scanning electrodesTx1 to Txm, an intersection capacity (Cxy), and an integral capacity(CINT) in the stated order, and an output voltage (VINT) of theintegrating circuit 10 drops.

In this case, VINT=VREF−Vstc*(Cxy/CINT) is satisfied.

(3) After the integration in the integrating circuit 10 has beencompleted, the switch (S2) turns off, and the switch (S3) turns on toprecharge the respective detection electrodes (Rx1 to Rxn) to 4V (aperiod A2 of FIG. 8). (4) The integrating operation in the integratingcircuit 10 of (2) is repeated, and the voltage is accumulated (periodsB2, in FIG. 8). (5) After the integration in the integrating circuit 10has been completed (period Bn in FIG. 8), the switch (S4) is turned onto sample and hold data by the sample-and-hold circuit 11 (period C inFIG. 8). Thereafter, the switch (S6) sequentially turns on, the ADconverter 12 conducts AD conversion, and stores RAW data for thescanning electrodes of Rx1 to Rxn in the memory (RAM).

When the AD converter 12 is an AD converter of 10 bits, the RAW dataranges from 0 (integration 0V) to 1023 (integration 4V). (6) Since theintersection capacity (Cxy) in the untouched state is larger than thatin the touched state, as indicated by Va and Vb in FIG. 6, a differenceoccurs in drop of the integration output voltage (VINT) of theintegrating circuit 10, and a threshold value is provided in thedifference to detect the touch.

In general, when the AD converter 12 is an AD converter of 10 bits, thedigital data obtained by subjecting a voltage Va illustrated in FIG. 6to AD conversion becomes 250 to 350 decimally. The digital data 250 to350 become an operating point in the normal detecting process.

FIG. 9 is a diagram illustrating timing in touch panel detectingoperation and pixel write operation in the in-cell type liquid crystaldisplay device. Referring to FIG. 9, T3 is a flyback period, VSYNC is avertical synchronizing signal, and HSYNC is a horizontal synchronizingsignal.

Symbol A in FIG. 9 shows pixel write timings from a first display lineto a 1280^(th) display line in a pixel write period (T4) of one frame,and symbol B in FIG. 9 shows touch panel detection timings in thecounter electrodes (CT1 to CT20) of each of the 20 divided blocks.

As illustrated in FIG. 9, the counter electrodes on an arbitrary displayline function as the scanning electrodes (TX), and the scanningoperation during the touch panel detection is conducted at a portiondifferent from gate scan for conducting pixel write.

As described in FIG. 9, the gate scan and the touch panel scan areimplemented on different display lines. However, because a parasiticcapacity is present between video lines and the counter electrodes (CT),and between the scanning lines and the counter electrodes (CT), thedetection sensitivity during the touch panel detection is deteriorateddue to a variation in the voltage (VDL) on the video lines, a rising ofthe scanning voltage (VGL), or noise occurring during falling of thescanning voltage (VGL).

Under the circumstances, in the in-cell type liquid crystal displaydevice which is the preamble of the present invention, the touchposition detecting operation is executed in a period of no variation inthe voltage (VDL) on the video lines, no rising of the scanning voltage(VGL), or no falling thereof.

FIG. 10 is a timing chart illustrating liquid crystal display paneldriving operation and the sensor electrode driving operation in thein-cell type liquid crystal display device which is the preamble of thepresent invention.

Referring to FIG. 10, vGL is a scanning voltage on the scanning lines,VDL is a video voltage on the video lines, Vcom is a counter voltage(also called common voltage) to be applied to the counter electrodes,Vstc is a touch panel scanning voltage, 1H is one horizontal scanningperiod, and Txs is a touch panel scanning start wait period.

In the in-cell type liquid crystal display device which is the preambleof the present invention, because dot inversion is employed as an ACdriving method, the counter voltage is a voltage of a constant potentialVcom.

In the in-cell type liquid crystal display device incorporating thetouch panel function into the liquid crystal display panel, because theband-like counter electrodes 21 illustrated in FIG. 2 also operate asthe scanning electrodes (Tx) for touch detection, the display operation(A in FIG. 10) of the liquid crystal display panel, and the touchposition detecting operation (B in FIG. 10) are completely divided intime, and synchronization control needs to be conducted.

As described above, in the in-cell type liquid crystal display devicewhich is the preamble of the present invention, the touch positiondetecting operation is executed in a period of no variation in thevoltage (VDL) on the video lines, no rising of the scanning voltage(VGL), or no falling thereof (period TA or period TB in FIG. 10).

FIG. 11 is a diagram illustrating the specifications of the registers1051 and 1052 illustrated in FIG. 4.

A register whose register name is TCP_TXDLY in FIG. 11 is the register1051 illustrated in FIG. 4, the parameter is unit delay time (t_txdly),and the unit delay time is set to 0 to 18.00 μs at 0.286 μs intervals.

Also, a register of TCP_TXMAXD illustrated in FIG. 11 is the register1052 illustrated in FIG. 4, the parameter is maximum delay time(t_txmaxd), and the maximum delay time is set to 0 to 18.00 μs at 0.286μs intervals. There is a need to satisfy the condition oft_txdly<t_txmaxd.

FIG. 12 is a diagram illustrating the touch panel scanning timing in thein-cell type liquid crystal display device which is the preamble of thepresent invention. Referring to FIG. 12, 1H is one horizontal scanningperiod, and TxH is a touch panel scanning period.

In the in-cell type liquid crystal display device which is the preambleof the present invention, when the touch panel scanning voltage (Vstc)is applied to the same scanning electrode (Tx) over a plurality ofhorizontal scanning periods by plural times (for example, 32 times), thetiming at which the touch panel scanning voltage (Vstc) is applied tothe scanning electrodes (Tx) is delayed by the unit delay time stored inthe register 1051 for each horizontal scanning period. However, the unitdelay time does not exceed the maximum delay time stored in the register1052.

In the in-cell type liquid crystal display device which is the preambleof the present invention, as illustrated in FIG. 12, in the firsthorizontal scanning period, the timing at which the touch panel scanningvoltage (Vstc) is applied to the scanning electrode (Tx) is a time pointafter a given wait time (t_txwait) has been elapsed from a rising timepoint of the horizontal synchronizing signal (Hsync). On the other hand,in the second horizontal scanning period, the timing at which the touchpanel scanning voltage (Vstc) is applied to the scanning electrode (Tx)is a time point (t_txwait+t_txdly) after a period obtained by adding theunit delay time (t_txdly) to the given wait time (t_txwait) has beenelapsed from the rising time point of the horizontal synchronizingsignal (Hsync). In an n(0≤n≤31)^(th) horizontal scanning period, thetiming at which the touch panel scanning voltage (Vstc) is applied tothe scanning electrode (Tx) is a time point (t_txwait+n×t_txdly) after aperiod obtained by adding n× unit delay time (n×t_txdly) to the givenwait time (t_txwait) has been elapsed from the rising time point of thehorizontal synchronizing signal (Hsync).

Thus, in the in-cell type liquid crystal display device which is thepreamble of the present invention, when the touch panel scanning voltage(Vstc) is applied to the same scanning electrode (Tx) over a pluralityof horizontal scanning periods by plural times (for example, 32 times),the timing at which the touch panel scanning voltage (Vstc) is appliedto the scanning electrodes (Tx) in the n(0≤n≤31)^(th) horizontalscanning period is represented by (t_txwait+delay; delay-n×t_txdly).Then, when (n×t_txdly) becomes equal to or larger than the maximum delaytime (t_txmaxd) (n×t_txdly≥t_txmaxd), (delay=delay-n×t_txdly) issatisfied.

Hereinafter, a description will be given of a setting example of theregister (TPC_TXDLY) 1051 and the register (TPC_TXMAXD) 1052 in thein-cell type liquid crystal display device which is the preamble of thepresent invention.

If touch panel scanning period (TxH)>one horizontal scanning period (1H)is satisfied,

[Example 1] register (TPC_TXDLY)=1, register (TPC_TXMAXD)=5, The numberof Delays=0, 1, 2, 3, 4, 0, 1,

[Example 2] register (TPC_TXDLY)=2, register (TPC_TXMAXD)=5, The numberof Delays=0, 2, 4, 1, 3, 0, 2,

If touch panel scanning period (TxH)<one horizontal scanning period (1H)is satisfied,

[Example 3] register (TPC_TXDLY)=9, register (TPC_TXMAXD)=10, The numberof Delays=0, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0, 9,

In a method illustrated in FIGS. 11 and 12, the timing at which thetouch panel scanning voltage (Vstc) is applied to the scanningelectrodes (Tx) is delayed by the unit delay time stored in the register1051 within a range not exceeding the maximum delay time stored in theregister 1052. However, the present invention is not limited to theabove example, but may employ the following method.

Hereinafter, a modified example of the in-cell type liquid crystaldisplay device which is the preamble of the present invention will bedescribed.

In the modified example of the in-cell type liquid crystal displaydevice which is the preamble of the present invention, 16 registers ofTXDLY1 [3:0] to TXDLY16 [3:0] are employed except for the registers 1051and 1052 illustrated in FIG. 4.

When it is assumed that k is an integral number (1≤k≤16) equal to orhigher than 1, and equal to or lower than 16, and n is an integralnumber (0≤n) equal to or higher than 0, TXDLYk [3:0] sets a time widthby which the timing at which the touch panel scanning voltage (Vstc) issupplied to the scanning electrodes (Tx) is delayed every (k+16n)horizontal scanning periods. That is, TXDLYk [3:0] sets the number ofunit delay time (t_txdly) from the time point after the given wait time(t_txwait) has been elapsed from the rising time point of the horizontalsynchronizing signal (Hsync) to the timing at which the touch panelscanning voltage (Vstc) is applied to the scanning electrodes (Tx).

As a result, as illustrated in FIG. 13, the delay time width to thetiming at which the touch panel scanning voltage (Vstc) is applied tothe scanning electrodes (Tx) after a given wait time (t_txwait) has beenelapsed from the rising time point of the horizontal synchronizingsignal (Hsync) can be set at random.

Table 1 shows an increasing/decreasing number (Δ) of the unit delay time(t_txdly) to the touch panel scanning period (TxH) when the time widthis 0 in which the values of 16 registers TXDLY1[3:0] to TXDLY16[3:0] areset to TXDLY1=0, TXDL2=5, TXDLY3=0, TXDLY4=1, TXDLY5=0, TXDLY6=15,TXDLY7=0, TXDLY8=7, TXDLY9=0, TXDLY10=2, TXDLY11=0, TXDLY12=8,TXDLY13=0, TXDLY14=4, TXDLY15=0, and TXDLY16=12, and a value of thetouch panel scanning period (TxH).

TABLE 1 1H 2H 3H 4H 5H 6H 7H 8H 9H 10H 11H 12H 13H 14H 15H 16H 17H UNITt_txdly 0 5 0 1 0 15 0 7 0 2 0 8 0 4 0 12 0 clk Δ 5 −5 1 −1 15 −15 7 −72 −2 8 −8 4 −4 12 −12 clk TxH 31.43 28.57 30.29 29.71 34.29 25.71 32.0028.00 30.57 29.43 32.29 27.71 31.14 28.86 33.43 26.57 us

In the normal touch panel, in order to reduce an influence of a noisesource of a terminal on which the touch panel is mounted on the touchdetection, the frequency for driving the electrodes (scanningelectrodes, detection electrodes) of the touch panel is adjusted.

On the other hand, in the in-cell type liquid crystal display deviceincorporating the touch panel function into the liquid crystal displaypanel, in order to prevent the influence of noise generated from theliquid crystal display panel, the touch panel is scanned with the use ofthe timing at which the liquid crystal display panel is not driven withreference to the synchronizing signal of the liquid crystal displaypanel. This leads to such a problem that the drive frequency of thetouch panel depends on the drive frequency of the liquid crystal displaypanel, and cannot be freely adjusted.

In the in-cell type liquid crystal display device which is the preambleof the present invention, and the modified example of the in-cell typeliquid crystal display device which is the preamble of the presentinvention, since the drive frequency of the touch panel can be freelyadjusted, the influence of the noise source of the terminal on which thetouch panel is mounted on the touch detection can be reduced.

However, there arises such a problem that when the exogenous noisehaving the noise frequency substantially equal to the integral multipleof the horizontal scanning frequency (exogenous noise frequency≈integralmultiple of horizontal scanning frequency) is entered, the integratingcircuit within the detector circuit induces false integration togenerate frictional touch ghost.

The feature of the in-cell type liquid crystal display device accordingto the present invention resides in that the above-mentioned fictionaltouch ghost is identified, and an influence of the fictional touch ghostin the touch detection is reduced.

FIG. 14 is a diagram illustrating a noise detection method of the touchpanel in the in-cell type liquid crystal display device according to anembodiment of the present invention.

In the touch panel according to this embodiment, the noise is detectedon the basis of a current flowing in the plurality of detectionelectrodes (Rx1 to Rx6) assuming that the scanning electrode of Txv ispresent in the scanning electrode (Tx0 to Tx7) of the actual touch panelas indicated by A in FIG. 14, and assuming that the touch panel scanningvoltage synchronous with the touch panel scanning voltage (Vstc) to beapplied to the scanning electrodes (Tx0 to Tx7) of the actual touchpanel is applied to the fictional counter electrode (Txv) as indicatedby B in FIG. 14.

In this example, the touch panel scanning voltage (Vstc) to thefictional counter electrode (Txv) is output from the touch panelscanning voltage generator circuit 103 illustrated in FIG. 2, but is notused.

The integrating circuit 10 is operated in synchronization with thefictional touch panel scanning voltage (Vstc) for the fictional counterelectrode (Txv) to detect the noise.

As illustrated in FIG. 15, if no noise is present, because electriccharge does not flow into the integrating circuit 10, the output voltage(VINT) of the integrating circuit 10 is maintained at 4V of thereference voltage (VREF). Therefore, a value of the RAW data after theoutput voltage (VINT) of the integrating circuit 10 has been subjectedto AD conversion by the AD converter 12 becomes 1023 decimally, and asindicated by A in FIG. 15, the value 1023 becomes the operating point atthe time of the noise detection. Also, symbol C in FIG. 15 is athreshold value (Th) line for noise determination, and it is determinedas the noise when a decimal value of the RAW data after the outputvoltage (VINT) of the integrating circuit 10 has been subjected to theAD conversion by the AD converter 12 is smaller than the threshold value(Th) line for the noise determination.

As illustrated in FIG. 16, when the noise frequency is noise other thanthe integral multiple of the horizontal scanning frequency (exogenousnoise frequency≈integral multiple of horizontal scanning frequency), theelectric charge flows into the integrating circuit 10. However, as aresult of offsetting the electric charge during the integration of theintegrating circuit 10, the output voltage (VINT) of the integratingcircuit 10 is maintained at about 4V of the reference voltage (VREF).Therefore, as indicated by B in FIG. 16, the value of the RAW data afterthe output voltage (VINT) of the integrating circuit 10 has beensubjected to the AD conversion by the AD converter 12 is maintained at avalue close to 1023 decimally.

As illustrated in FIG. 17, when the noise frequency is noisesubstantially equal to the integral multiple of the horizontal scanningfrequency (exogenous noise frequency≈integral multiple of horizontalscanning frequency), an inflow direction of the electric charge into theintegrating circuit 10 periodically slants in one direction, and theoutput voltage (VINT) of the integrating circuit 10 is largely changed.Therefore, as indicated by C in FIG. 17, the RAW data value after theoutput voltage (VINT) of the integrating circuit 10 has been subjectedto the AD conversion by the AD converter 12 is largely changed.

With the decimal value 1023 as the operating point, as indicated by B inFIG. 17, it is determined as the noise if the decimal value of the RAWdata after the output voltage (VINT) of the integrating circuit 10 hasbeen subjected to the AD conversion by the AD converter 12 falls belowthe threshold value (Th) line for the noise determination indicated by Cin FIG. 17.

As illustrated in FIG. 17, when it is determined as the noise, thefictional touch ghost is then identified.

A difference in the operating point of the RAW data is used foridentification of the fictional touch ghost. That is, the RAW data isallowed to pass through the averaging filter to extract the operatingpoint of the RAW data.

FIGS. 18A and 18B are graphs illustrating the RAW data of the detectionelectrodes where noise is detected, and data that has passed through anaveraging filter in the touch panel according to this embodiment.

In this embodiment, an AC charger noise is assumed, and the fictionaltouch ghost caused by the AC charger noise is generated on the samedetection electrode. Therefore, FIGS. 18A and 18B illustrate graphs whenthe noise is detected in the detection electrode of Rx6 illustrated inFIG. 14.

Referring to FIGS. 18A and 18B, Tx0_Rx6 represents the RAW data obtainedfrom the detection electrode of Rx6 when the touch panel scanningvoltage (Vstc) is applied to the scanning electrode of Tx0.

Likewise, Tx1_Rx6 represents the RAW data obtained from the detectionelectrodes of Rx6 when the touch panel scanning voltage (Vstc) isapplied to the scanning electrode of Tx1. Tx2_Rx6 represents the RAWdata obtained from the detection electrodes of Rx6 when the touch panelscanning voltage (Vstc) is applied to the scanning electrode of Tx2.Tx3_Rx6 represents the RAW data obtained from the detection electrodesof Rx6 when the touch panel scanning voltage (Vstc) is applied to thescanning electrode of Tx3. Tx4_Rx6 represents the RAW data obtained fromthe detection electrodes of Rx6 when the touch panel scanning voltage(Vstc) is applied to the scanning electrode of Tx4. Tx5_Rx6 representsthe RAW data obtained from the detection electrodes of Rx6 when thetouch panel scanning voltage (Vstc) is applied to the scanning electrodeof Tx5. Tx6_Rx6 represents the RAW data obtained from the detectionelectrodes of Rx6 when the touch panel scanning voltage (Vstc) isapplied to the scanning electrode of Tx6. Tx7_Rx6 represents the RAWdata obtained from the detection electrodes of Rx6 when the touch panelscanning voltage (Vstc) is applied to the scanning electrode of Tx7.

FIG. 18B illustrates the RAW data after the RAW data shown in the graphof FIG. 18A has passed through an averaging filter.

As illustrated in FIG. 18B, an electrode (scanning electrodeintersecting with the detection electrodes of Rx6) having the maximumvalue of the operating point in the RAW data at the time of detectingthe noise is determined as the actual touch electrode, and the electrodeportion having the operating point lower than a ghost determinationthreshold line (Th1) is determined as the ghost. In FIG. 18B, Arepresents an actual touch electrode, B is an electrode adjacent to thetouch electrode, and C is an electrode in which the fictional touchghost is generated.

FIG. 19 is a flowchart illustrating a touch position detecting processin the liquid crystal display device according to the embodiment of thepresent invention.

When the touch position detecting process is executed, the integratingcircuit 10 operates in synchronization with the fictional touch panelscanning voltage (Vstc) for the fictional counter electrode (Txv) todetermine whether the noise is present, or not (Step S110).

If it is determined as no noise in Step S110, the normal touch positiondetecting process is executed (Step S111), and the coordinates of thetouch position is reported (S112).

If it is determined that the noise is present in Step S110, an exceptionprocess (averaging filtering process) is executed (Step S113), and it isdetermined whether the frictional touch ghost is identifiable, or not(Step S114).

If the fictional touch ghost is identifiable in Step S114, the touchposition detecting process is executed with reference to information onthe fictional touch ghost, and the coordinates of the touch position arereported (S115).

If the fictional touch ghost is unidentifiable in Step S115, the touchposition detecting process is not executed, and the coordinates of thetouch position are not also reported (S116).

As has been described above, this embodiment can reduce an influence ofthe fictional touch ghost generated by allowing the integrating circuitwithin the detector circuit to induce false integration with enteringthe exogenous noise having the noise frequency substantially equal tothe integral multiple of the horizontal scanning frequency (exogenousnoise frequency a integral multiple of horizontal scanning frequency),without the addition of hardware means, but with only software.

In this embodiment, the above-described in-cell type liquid crystaldisplay device which is the preamble of the present invention can becombined with the technique in which the drive frequency of the touchpanel is freely adjusted in the modified example of the in-cell typeliquid crystal display device which is the preamble of the presentinvention, to enable a more reduction in the influence of the noise.Also, the present invention can be applied to a general in-cell typeliquid crystal display device.

The invention made by the present inventors has been described in detailon the basis of the embodiments, but the present invention is notlimited to the above embodiments, and can be variously changed withoutdeparting from the spirit of the present invention.

While there have been described what are at present considered to becertain embodiments of the invention, it will be understood that variousmodifications may be made thereto, and it is intended that the appendedclaim cover all such modifications as fall within the true spirit andscope of the invention.

What is claimed is:
 1. A display device comprising: a display panelincluding a plurality of pixels, a plurality of detection electrodes,and common electrodes divided into M blocks when M is an integral numberof 2 or more (M≥2); a driver circuit applying a common voltage and atouch panel scanning voltage to the common electrodes of each of the Mdivided blocks; and a detector circuit detecting a touch signal of theplurality of detection electrodes, wherein the common electrodes of eachof the M divided blocks are shared with the respective pixels, and arealso used as scanning electrodes, wherein the driver circuitsequentially applies the touch panel scanning voltage to the commonelectrodes of each of the M divided blocks, wherein the detector circuitdetermines: in a normal touch detection process, a touch event bydetecting the touch signal of the plurality of detection electrodes whenthe touch panel scanning voltage is applied to the common electrodes ofeach of the M divided blocks, in a ghost touch detection process, aghost touch event by detecting the touch signal of the plurality ofdetection electrodes without applying the touch panel scanning voltageto the M divided blocks, wherein a threshold value for determining thetouch event of the normal touch detection process is different from thatfor determining the ghost touch event of the ghost touch detectionprocess, wherein the detector circuit includes: a plurality ofintegrating circuits provided each of the plurality of detectionelectrodes, and an AD converter that converts an output voltage of theplurality of integrating circuits into digital data, wherein each of theintegrating circuits integrates a current of the respective detectionelectrodes, and wherein the detector circuit determines the touch eventwith a first operating point of the AD converter, and the ghost touchevent with a second operating point of the AD converter.
 2. The displaydevice according to claim 1, wherein the first operating point is avalue closer to the least significant bit than an intermediate valuebetween the least significant bit and the most significant bit in thedigital data converted by the AD converter, and the second operatingpoint is the most significant bit in the digital data converted by theAD converter.
 3. The display device according to claim 2, wherein thetouch event is determined when the digital data obtained by convertingan integral value of the plurality of integrating circuits for each ofthe detection electrodes by the AD converter is a value between a firstoperating point and the most significant bit, and when a differencebetween the value of the digital data and the first operating point islarger than a first threshold value.
 4. The display device according toclaim 2, wherein the ghost touch event is determined when the digitaldata obtained by converting an integral value of the plurality ofintegrating circuits for the detection electrode by the AD converter isa value between a second operating point and the least significant bit,and when a difference between the value of the digital data and thesecond operating point is larger than a second threshold value.
 5. Thedisplay device according to claim 2, wherein the digital data to beconverted by the AD converter is data of 10 bits, wherein the firstoperating point is a value of 250 to 350 decimally, and wherein thesecond operating point is a value close to 1023 decimally.
 6. Thedisplay device according to claim 1, further comprising: an averagingfilter which averages the digital data obtained by converting theintegral value of the integrating circuits corresponding to thedetection electrode when the ghost touch event is determined in theghost touch detection process.
 7. A display device comprising: a displaypanel having a plurality of pixels arranged in a matrix, a plurality ofdetection electrodes, and common electrodes arranged along therespective pixels and divided into M blocks when M is an integral numberof 2 or more (M≥2); a driver circuit applying a common voltage and atouch panel scanning voltage to the common electrodes of each of the Mdivided blocks; and a detector circuit detecting a touch signal of theplurality of detection electrodes, wherein the common electrodes of eachof the M divided blocks are shared with the respective pixels of aplurality of continuous display lines, and are also used as scanningelectrodes, wherein the driver circuit sequentially applies the touchpanel scanning voltage to the common electrodes of each of the M dividedblocks, and wherein the detector circuit is configured to: determine atouch detected by the touch signal of the plurality of detectionelectrodes when the touch panel scanning voltage is applied to thecommon electrodes of each of the M divided blocks; determine a noisedetected by the touch signal of the plurality of detection electrodes,assuming that an (M+1)^(th) common electrode is present for the commonelectrodes of each of the M divided blocks, and assuming that a touchpanel scanning voltage synchronous with the touch panel scanning voltageapplied to the common electrodes of each of the M divided blocks isapplied to the (M+1)^(th) common electrode; and determine a ghost touchwhen the noise is determined by the detector circuit, wherein a firsttouch position detecting process is executed when the noise is notdetermined by the detector circuit, wherein when the noise is determinedby the detector circuit, if the ghost touch is determined by thedetector circuit, a second touch position detecting process is executed,and wherein when the noise is detected by the detector circuit, if theghost touch is not determined by the detector circuit, the second touchposition detecting process is not executed.
 8. The display deviceaccording to claim 7, wherein the detector circuit includes: a pluralityof integrating circuits provided every plural detection electrodes; andan AD converter that converts an output voltage of the plurality ofintegrating circuits into digital data.
 9. The display device accordingto claim 8, wherein each of the integrating circuits integrates acurrent of the respective detection electrodes when the touch panelscanning voltage is applied to the common electrodes of each of the Mdivided blocks, and when a fictional touch panel scanning voltage isapplied to the fictional (M+1)^(th) common electrode.
 10. The displaydevice according to claim 8, wherein the detector circuit is configuredto determine the touch with a first operating point that is a valuecloser to the least significant bit than an intermediate value betweenthe least significant bit and the most significant bit in the digitaldata converted by the AD converter, and the detector circuit isconfigured to determine the ghost touch with a second operating pointthat is the most significant bit in the digital data converted by the ADconverter.
 11. The display device according to claim 10, wherein thetouch is determined when the digital data obtained by converting anintegral value of the plurality of integrating circuits for each of thedetection electrodes by the AD converter is a value between a firstoperating point and the most significant bit, and when a differencebetween the value of the digital data and the first operating point islarger than a first threshold value, the ghost touch is determined whenthe digital data obtained by converting an integral value of theplurality of integrating circuits for the detection electrode by the ADconverter is a value between a second operating point and the leastsignificant bit, and when a difference between the value of the digitaldata and the second operating point is larger than a second thresholdvalue.